On Wed, Jan 29, 2020 at 11:19:47AM -0800, William Tu wrote:
> On Wed, Jan 29, 2020 at 3:25 AM Flavio Leitner <[email protected]> wrote:
> >
> > On Tue, Jan 28, 2020 at 03:23:02PM -0800, Yifeng Sun wrote:
> > > Sure.
> > >
> > > Firstly, make sure userspace-tso-enable is true
> > > # ovs-vsctl get Open_vSwitch . other_config
> > > {dpdk-init="true", enable-statistics="true", pmd-cpu-mask="0xf",
> > > userspace-tso-enable="true"}
> > >
> > > Next, create 2 VMs with vhostuser-type interface on the same KVM host:
> > > <interface type='vhostuser'>
> > > <mac address='88:69:00:00:00:11'/>
> > > <source type='unix'
> > > path='/tmp/041afca0-6e11-4eab-a62f-1ccf5cd318fd' mode='server'/>
> > > <model type='virtio'/>
> > > <driver queues='2' rx_queue_size='512'>
> > > <host csum='on' tso4='on' tso6='on'/>
> > > <guest csum='on' tso4='on' tso6='on'/>
> >
> > I have other options set, but I don't think they are related:
> > <host csum='on' gso='off' tso4='on' tso6='on' ecn='off'
> > ufo='off' mrg_rxbuf='on'/>
> > <guest csum='on' tso4='on' tso6='on' ecn='off' ufo='off'/>
>
> Is mrg_rxbuf required to be on?
No.
> I saw when enable userspace tso, we are setting external buffer
> RTE_VHOST_USER_EXTBUF_SUPPORT
Yes.
> Is this the same thing?
No.
mrg_rxbuf says that we want the virtio ring to support chained ring
entries. If that is disabled, the virtio ring will be populated with
entries of maximum buffer length. If that is enabled, a packet will
use one or chain more entries in the virtio ring, so each entry can
be of smaller lengths. That is not visible to OvS.
The RTE_VHOST_USER_EXTBUF_SUPPORT tells how a packet is provided
after have been pulled out of virtio rings to OvS. We have three
options currently:
1) LINEARBUF
It supports data length up to the packet provided (~MTU size).
2) EXTBUF
If the packet is too big for #1, allocate a buffer large enough
to fit the data. We get a big packet, but instead of data being
along with the packet's metadata, it's in an external buffer.
<packet [packet metadata] [ unused buffer ]>
+---> [ big buffer]
Well, actually we make partial use of unused buffer to store
struct rte_mbuf_ext_shared_info.
3) If neither LINEARBUF nor EXTBUF is not provided (default),
vhost lib can provide large packets as a chain of mbufs, which
OvS doesn't support today.
HTH,
--
fbl
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